There are many different ways to construct gas turbine combustion chambers. One of these is the use of annular combustion chambers, to which the present invention relates, inter alia. These are annular combustion chambers which are arranged in a substantially rotationally symmetrical manner around the rotor of the gas turbine between the compressor and turbine. A combustible gas mixture is introduced into the annular combustion chamber via normally a large number of burners, and this gas mixture burns therein and flows into the turbine as an annular flow. The substantially annular space is delimited to the inside, i.e. to the rotor side, by a so-called inner shell or inner burner casing, and to the outside by a so-called outer shell or outer burner casing. These shells often comprise a plurality of individual portions which are welded or mechanically joined to each other and thereby form the structural unit of a gas turbine. As is known from EP 1662201, the individual portions may have a double-walled design, such that a flow of cooling air can be guided between the substantially parallel walls.
In order to protect the inner and outer burner casings against the high temperatures produced within the combustion chamber, it is generally known to coat the inner surfaces exposed to the heat with a thermal barrier coating (TBC), for example zirconia partially stabilized with yttria (YSZ), which can withstand a thermal shock of up to 1150° C. and material fatigue. The YSZ coating can be applied by plasma spraying or by electron beam vapor deposition. Although these TBCs are available at all times, they cannot be applied to a weld seam if common materials are used as the starting material, as is known from DE 10 2007 001 835. The life of the welded joint between the portions of the burner casing is therefore extremely limited.
The high temperatures and the evolution of heat in the combustion chamber mean that the shells are exposed to high thermal loads. In order to ensure a sufficient life in spite of the high thermal loading, annular combustion chambers which employ different cooling methods and are also mostly combined with thermal barrier coatings or protective shields have been developed.
Thus, by way of example, DE 10 2007 001 835 (already mentioned above) describes a combustion chamber casing, in which the outer shell is formed from two half-shells welded to each other at a joining line, and in which the inner shell is formed from two half-shells likewise welded to each other at a joining line. In order to make it possible to guarantee protection of the weld seam, the half-shells each have a joining flange, at the joining line, which is remote from the hot side and serves to join the half-shells to the weld seam. In addition, a heat shield is arranged on the hot-gas side of this weld seam, offset from the latter, and protects the weld seam against the high temperatures.
WO 2009/040286 discloses a similar combustion chamber design. In order to protect the weld seam, this document proposes a film cooling means which is guided deliberately along the weld seam by providing an indentation, which points away from the hot side, in the region of the weld seam.